360 stock intake manifold on a stock 318?

[66fs]

... We talk about "suction" but in reality there is no such thing. What there REALLY is, is the atmospheric air pressure pushing into a void, an evacuated space...

You are mechanically producing a vacuum with the piston. Close off your inlet and this will become apparent. There is a atmospheric air pressure component but there is more to it than that.

 

[mguner]

A less dramatic but still viable improvement that will piss off the average looser on the street is the 360 2bbl swap. It looks stock but flows better and great bottom end. You'd be surprised how much power a 318 can make with 300 CFM.... :tongue9:

 

[RustyRatRod]

I understand that. I was trying to over simplify it.

It's easy to prove my point though, that air does not "pile up" around a smaller intake port.

Stick a paper towel roll over your mouth and suck air in. Every bit of the air you can suck in goes in your mouth. It does not pile up around it from a port mismatch. It simply doesn't happen that way.

Actually, Rob, on this one you are incorrect. There is not a "thing" called vacuum, in otherwords some invisible magic fluid, anymore that there is a thing called dark (lack of light) or something in a glass that replaces half full to "fillup" and "be" half empty.

The fact is that the pistons PUSH the air out of the cylinder during exhaust, and when the intake stroke is happening, atmospheric pressure from outside is pushing air into the empty, evacuated cylinder.

We talk about "suction" but in reality there is no such thing. What there REALLY is, is the atmospheric air pressure pushing into a void, an evacuated space.

But the more important point is that a reasonably "big" manifold such as a street 340/360 works well on small port 318 heads for a good solid performance "bolt on" jump.

These little guys DO also need a bit more cam, and of course exhaust as stated.

It's really too bad that "Ma" didn't make these engines more easily interchangeable, AKA 360 heads on a teen.

 

[sireland67]

If you can get the stock 4bbl intake cheap, buy it.
They will work.
FYI I have a LD4B on my old farm truck with a 625 Demon and it was night and day difference between the BBD 2b.
Also the BBD 2b was rebuilt by me and ran excellent.

4bbl just made a huge difference, no other changes.

 

[sorewrist1]

does a horse push a cart or pull a cart? He pushes into the halter

 

[Marcohotrod]

I think the factory 318 with 4 barrel came with 360 heads? and the old Edelbrock 318 Streetmaster aluminum 4 barrel intake worked great and had the small ports

 

[AJ/FormS]

People tell me that Ma never made a smallport TQ manifold for automotive apps. Well I spotted such a manifold in a guys garage many years ago. Complete with an EGR valve on it.I bought it on-the-spot. It works awesome on my winter motor.Better than anything I ever put on a LC teener. He didn't know what I came off. And since it was smallport, it was cheap. Score!
I think 69Cuda posted a chart that says the small TQ flows 200ish on the front side.Whatever it might be, it's very sharp on the primaries.

 

[Ddaddy]

Air flows from higher pressure to lower pressure. There is no such thing as vacuum, only pressure.

The issue with a mismatch on ports is turbulence. The turbulence increases the boundary region and causes the free laminar flow region to become reduced. This in turn increases overall resistance to flow volume.

Resistance to flow in an air pump reduces efficiency and in an internal combustion engine, reduces HP and performance.

Suck air through a smooth straw and then one of the same diameter that is corrugated. You will find that the corrugated one requires more energy to pull the same volume of air through.

The same is true on an engine, more energy required to pull a specific volume air means less energy output from the system to drive the wheels. (reduced performance/HP).

It's all just simple physics.

 

[RustyRatRod]

But we're not talkin about something corregated. This is stupid. We're only talking about one port size on top of another.....and they are really not all that different in size.

Like I said. Chrysler did it MILLIONS of times and it worked fine. They weren;t worried too much about any turbulance.

That's it for me on this.

 

[AJ/FormS]

They make AR (Anti-Reversion ) headers to exploit the mismatch. I've even seen them on motorcycles and snowmobiles.

 

[Abodybomber]

They make AR (Anti-Reversion ) headers to exploit the mismatch. I've even seen them on motorcycles and snowmobiles.

Been a while,since I have seen a new set of those.. Mid 80's,IIRC... As for the O.P.: I would do a stock 360 intake( or find even a Holley Street Dominator intake,or a SP2P Edelbrock,even...) .One of these,dual exhaust, & a distributor recurve,should get it done...

 

[Infecteddog]

I think the factory 318 with 4 barrel came with 360 heads? and the old Edelbrock 318 Streetmaster aluminum 4 barrel intake worked great and had the small ports

At least the E48 motors did- the common cop car/towing/HP motor.

It's really too bad that "Ma" didn't make these engines more easily interchangeable, AKA 360 heads on a teen.

Yes there's a compression drop going to 360 heads on a 318. It drops down near where the compression of those 360s was. Outside of a handful most 360s were dismal low compression right down to where most people try to keep 318s away from. That's why Chrysler put 360 heads on them and called those 360 heads an improvement over the 302s. Don't think the E48s had just the 360-LD cam though.

What's a shame is that they didn't standardize more into the 318 line following the introduction of better parts on the 340 and 360 lines.

A less dramatic but still viable improvement that will piss off the average looser on the street is the 360 2bbl swap. It looks stock but flows better and great bottom end. You'd be surprised how much power a 318 can make with 300 CFM.... :tongue9:

Course, you go through as much work since the intake's different along with the carb unless you put an adapter on it. But yeah, the comment was exact for a reason- I don't think it's very much too insufficient, but insufficient at all is enough to be a negative.

 

[sr71mopar]

Run it.

 

[kaytbugsdad]

I did the 360 2bbl swap on my 318(out of a 77 B200 van, Holley 2 bbl), and I love it!!! So much smoother to drive, throttle response is right now, and gas mileage didn't change at all (not that I care about gas mileage)....... Of course, maybe the BBD I had on the 318 was a piece of crap......